1. Field of the Invention
The present invention relates to a sheet processing apparatus which loads and processes punched sheets provided with holes as well as to an image forming apparatus equipped with the sheet processing apparatus.
2. Description of the Related Art
Conventionally, image forming apparatus, such as copiers, printers, facsimile machines and multi-functional peripherals, which form images on sheets are sometimes equipped with a sheet processing apparatus adapted to load the sheets one after another onto a processing tray once after an image is formed on the sheets by an image forming unit, and width-adjust the sheets on the processing tray, and then discharge the sheets (Japanese Patent Application Laid-Open No. 2003-238021).
The conventional sheet processing apparatus are designed to load a succeeding sheet on preceding punched sheets already loaded on the processing tray even when width-adjusting punched sheets in which filing holes are formed near a lateral edge along a sheet conveying direction.
However, when discharged onto the preceding punched sheets, the succeeding sheet is loaded on top of the preceding punched sheets, with the leading edge of the succeeding sheet sliding over the preceding punched sheets. Consequently, the leading edge of the succeeding sheet could get caught in holes of one or more of the preceding punched sheets, thereby pushing the preceding punched sheet(s) out of the processing tray.
In particular, if the leading edge of the succeeding sheet is curled toward the punched sheets or if hole edges are burred as a result of punching, the leading edge of the succeeding sheet is liable to get caught in holes of the punched sheets. Also, a leading edge corner of the succeeding sheet can at times get bent when caught in holes of the punched sheets.
Thus, it is difficult for the conventional sheet processing apparatus to apply a width adjustment to punched sheets before discharging the punched sheets.